moody (adj.)

Old English modig "brave, proud, high-spirited, impetuous, arrogant," from Proto-Germanic *modago- (source also of Old Saxon modag, Dutch moedig, German mutig, Old Norse moðugr); see mood (n.1) + -y (2). Meaning "subject to gloomy spells" is first recorded 1590s (via a Middle English sense of "angry").